Continuous development of wireless communications technologies poses increasingly high requirements on network capacity and network coverage, and more requires related communications devices to meet requirements of low costs and strong environmental adaptability. In addition, backhaul (backhaul) systems between base stations and between a base station and a core network, especially a wireless backhaul system between base stations (shown in FIG. 1), have extremely high requirements on transmission reliability, and are faced with greater challenges due to channel complexity in a wireless transmission environment. Therefore, the industry gradually analyzes and applies a multi-antenna array beamforming (beamforming) technology to a wireless backhaul (backhaul) system device, so as to further expand space-domain freedom and obtain an interference suppression capability by using the beamforming technology.
Beamforming is a signal processing technology. In this technology, an antenna array is formed by using a plurality of antenna array elements, and weighting processing is separately performed on signals at each antenna array element by using an advanced signal processing algorithm, so that the antenna array is aligned with a direction of a wanted signal in real time, and a directional-null antenna is formed in an interference direction to suppress an interference signal, thereby increasing a signal-to-noise ratio and improving system performance.
Currently, a commonly used beamforming method includes analog beamforming (analog beamforming, ABF) or digital beamforming (digital beamforming, DBF). A specific implementation architecture in a DBF solution is shown in FIG. 2a, and a specific implementation architecture in an ABF solution is shown in FIG. 2b. 
When the beamforming technology is applied to a wireless communications backhaul system, it is found that in the DBF solution, independent signal streams R1(n) to RN(n) at each antenna array element can be obtained, so that a beamforming weight can be adaptively obtained according to signal characteristics of each antenna array element, to perform beamforming. Therefore, relatively good interference suppression performance can be obtained. However, the DBF solution requires that each antenna array element should have an independent digital signal processing channel, that is, signals received and transmitted by each antenna array element are required to be processed by an independent digital to analog converter (digital to analog converter, DAC) and an independent analog to digital converter (analog to digital converter, ADC) before the signals are transmitted to a digital side. As a result, costs are relatively high, a structure is difficult to implement. Therefore, the DBF solution is difficult to be widely applied to backhaul systems. In the ABF solution, each antenna array element does not have an independent digital signal processing channel, but instead analog signals are combined by using a combiner or analog signals are distributed by using a power splitter. Therefore, the ABF solution has significant cost advantages and a simple architecture. However, because in the ABF solution, there is no independent DAC or ADC between each antenna array element and a digital side, a receive end receives superimposed signals r(n) from a plurality of antenna array elements, and an independent signal stream at each antenna array element cannot be obtained. As a result, a beamforming weight cannot be adaptively obtained according to signal characteristics of each antenna array element, and beamforming can be performed only by using a preset beamforming weight. This leads to relatively poor interference suppression performance, and therefore the ABF solution is also difficult to be widely applied to backhaul systems.